8 



HJALMAR BROCH. 



[REP. OF THE "MICHAEL SARS" NORTH 



Periphylla regina is distinguished from the preceding 

 species mainly by its rounded bell, which contains the 

 uniformly rounded apex of the stomach. Another cri- 

 terion is found in the semiglobular pedalia, which con- 

 trast sharply with the rather oblong pedalia of Periphylla 

 hyacinthina. Maas 1 ) regards the colour as a good specific 

 character; his opinion seems mainly to be based on 

 sketches drawn by Alexander Agassiz. Vanhoffen 2 ) 

 agrees with Maas in this respect, although, as Maas 3 ) 

 and Bigelow 4 ) point out later, he has not shown the 

 differences in colour clearly in his excellent figures. On 

 this point I cannot agree with previous investigators, for 

 in the "Michael Sars" material (which is excellently pre- 

 served and came into my hands in quite a fresh condition, 



the colours being as vivid as in the living animals) no 

 difference whatever could be observed in the colours 

 of Periphylla regina and Periphylla hyacinthina. The 

 brownish and bluish velvety black covering the subum- 

 brella had mostly retained its metallic appearance, but 

 it was in fact impossible to find more differences than 

 in Vanhoffen's figures. The figure in Maas's paper, 

 differing interestingly from most other deep-sea Medusae, 

 must have been drawn from a specimen with an unusu- 

 ally variety of colours. 



Periphylla regina is only sparingly represented in 

 the material from the "Michael Sars"; the specimens 

 which can be identified with certainty are given in the 

 following table: — 



Stalion 



Lat. N 



Long W 



Depth 

 in metres 



Number 

 of specimens 



Larger diameter 

 above the furrow 



19 (Mediterranean) 



36° 5' 



4° 42' 



900-0 



2 



10 and 14 mm 



49 b 



29° 8' 



25° 16' 



1500 





40 mm 



56 



36° 53' 



29° 47' 



1500 





34 „ 



62 



36° 52' 



39° 55' 



1250 





15 5 „ 



63 



36° 5' 



43° 58' 



4500-1500 





55 „ 



64 



34° 44' 



47° 52' 



1500 





35 „ 



84 



48° 4' 



32° 25' 



1250 





37 . 



92 



48° 29' 



13° 55' 



1500 





43 „ 



From these data we are compelled to consider Peri- 

 phylla regina as a veritable deep-sea Medusa, which has 

 its optimum far below the reach of daylight, a fact making 

 it probable that the metallic brownish or bluish black 

 colour is the predominating one, being seen also in full- 

 grown specimens of Atolla, Crossota and other inhabitants 

 of great oceanic depths. The information is too defective 

 to enable us to form an idea as to the upper and lower 

 bathymetrical limits of the species. We can only state 

 that it is one of the deeper living species of the genus, 

 and indeed belongs to the abyssal region of the ocean. 



The geographical range of Periphylla regina seems 

 to be almost as wide as that of P. hyacinthina, but we 

 notice an interesting difference. P. hyacinthina has been 

 found in all the great oceans and in the antarctic seas, 



where it is was taken by the "Southern Cross" and the 

 "Discovery", 5 ) its northernmost locality being far up in 

 Baffin's Bay. P. regina, on the other hand, has only 

 been found in the tropical and subtropical parts of the 

 ocean, and once 6 ) in the subantarctic region. It has not 

 been taken north of Wyville Thomson ridge (com- 

 pare the map, fig. 5 on p. 7), and thus affords further 

 evidence that this ridge forms a barrier separating the 

 arctic deep-sea region from the Atlantic abyssal region; 7 ) 

 that this may not be due to depth alone is shown by 

 the fact that the "Michael Sars" took Periphylla regina 

 in the Mediterranean just inside Gibraltar Strait (Stat. 9). 

 Thus in this case the shallower barrier at Gibraltar has 

 not the same limiting power as the deeper Wyville 

 Thomson ridge. 



*) Die Medusen (Rep. Explor. West Coasts of Mexico, Central and South America, and off the Galapagos Islands. — Mem. Mus. 

 Comp. Zoo!., Vol. XXIII) Cambridge U. S. A. 1897, p. 64, pi. X. 



2 ) Deutsche Tiefsee-Expedition, p. 23. 



3 ) Meduses provenant des campagnes des yachts Hirondelle et Princesse Alice, p. 46. 

 *) The Medusae (Mem. Mus. Comp. ZooL, Vol. XXXIII), p, 26. 



s ) Browne: Medusae (National Antarctic Expedition. Natural History, Vol. V), London 1810, p. 42. 

 ) Haeckel: Report of the Deep-Sea Medusae. (Zool. Chall. Exp., Vol. 4). London 1881, p. 85. 

 7 ) Comp. Broch : Die Hydroiden der arktischen Meere (Fauna arctica, Bd. V), Jena 1910, p. 230. 



